1. Field of the Invention
The present invention relates to a reducer of an electric power steering apparatus, and more particularly, a reducer of electric power steering apparatus in which a damping member is provided on an outer circumference surface of a bearing bush so that impact between a worm shaft bearing and the bearing bush is dampened, and noise generated at a time of impact is reduced.
2. Description of the Prior Art
FIG. 1 is a cross-sectional view illustrating a conventional reducer of an electric power steering apparatus.
As illustrated in FIG. 1, a conventional reducer 100 of an electric power steering apparatus is provided with a worm shaft 103 which is formed with a worm 101 on an outer circumference surface thereof. Worm shaft bearings 105a and 105b are installed on both ends of the worm shaft 103, respectively, so as to support the worm shaft 103. A plug bolt 107 is fastened between a damping coupler 109 and the worm shaft bearing 105b so as to prevent the worm shaft bearing 105b from being moved in an axial direction of the worm shaft 103. The plug bolt 107 is anchored by a plug nut 111.
The worm shaft 103 is connected with a motor shaft 115 of a motor 113 via a damping coupler 109 such that the worm shaft 103 is rotated when the motor 113 is driven.
In addition, a worm wheel 117 is provided on one diametric side of the worm 101 to be tooth-engaged with a worm 101 formed on the worm shaft 103. The worm wheel 117 is mounted on a steering shaft 119 configured to transmit a rotation force of a steering wheel (not illustrated) operated by a driver, so that a rotation force of the worm shaft 103 generated by driving the motor 113 is transmitted to the steering shaft 119.
The worm shaft 103, the worm wheel 117 etc. are disposed within a gear housing 121 and the motor 113 configured to provide a driving force to the worm shaft 103 is provided on a side of the gear housing 121, in which a motor cover 123 is coupled to the gear housing 121 through a bolt 125.
Balls 131 are interposed between an inner wheel 127 and an outer wheel 129 of the worm shaft bearing 105b so as to support the rotation of the worm shaft 103 connected with the motor shaft 115 of the motor 113.
The reducer of the electric power steering apparatus configured as described above controls the driving of the motor 113 by an electronic control unit provided in a vehicle according to a vehicle driving condition, the rotation force of the worm shaft 103 generated by driving the motor 113 is added to the rotation force of the steering wheel operated by the driver and transmitted to the steering shaft 119 so that the driver's steering operation state can be smoothly and stably maintained.
However, such a conventional reducer of an electric power steering apparatus causes problems in that when the endurance of the worm shaft, which is rotated by driving the motor, and the worm, which is wheel tooth-engaged with the worm formed on the worm shaft, is consumed, a clearance is increased, which not only causes occurrence of noise, but also causes a steering-assist force assisting in the driver's steering wheel operating force to be incorrectly provided.